Methods and devices for storing and dispensing liquids

ABSTRACT

In a liquid handling system including a liquid handling substrate having a plurality of channels for conducting a liquid sample in said substrate, where the channels terminate in a plurality of exit ports in an outer surface of the substrate for transfer of a quantity of the liquid sample. The handling system also includes a liquid storage and dispensing substrate having a plurality of separable cartridges corresponding to the channels, with each cartridge terminating at a microelectro mechanical system (MEMS) comprising a laminate of glass, silicon and a piezoelectric substance. The handling system further includes a liquid detecting system comprising a light emitting diode and a photo-detector, where each channel includes a reservoir in communication with a corresponding cartridge creating an interface therebetween. The handling system enables a method for storing and dispensing liquids including drawing a liquid sample into the channels either by capillary action, vacuum, electoosmotic flow, a minipump or any combination thereof, storing the liquid sample into the cartridge, and dispensing the liquid sample.

RELATED APPLICATION

This application is a continuation of U.S. application Ser. No.09/827,570, filed Apr. 5, 2001, which claims priority to U.S.application Ser. 60/194,586, filed Apr. 5, 2000, which is incorporatedherein by reference in its entirety.

BACKGROUND OF THE INVENTION

1. Field of the Present Invention

The present invention generally relates to devices and methods forstoring and dispensing quantities of liquids. More specifically, thepresent invention uses a macro/micro interface and a microelectromechanical system to store and dispense chemical and biological liquidsin minute quantities.

2. Description of the Related Art

Until the relatively recent advent of combinatorial chemistry andgenetic research spawned the need for high-throughput analyzing andscreening techniques, researchers performed such assays using vials,tubes and beakers. However, with ever more substances available viasynthesis or via combinatorial techniques for testing, the need hasarisen to test the possible role of thousands, or even millions ofsubstances, in comparable numbers of possible reactions. Miniaturizationhas been identified as a promising path to more efficient, e.g. lessexpensive, chemical, and in particular, drug, analysis and screening.Discussions of various aspects of such analysis and screening techniquesare found in J. D. Devlin, ed., High Throughput Screening: The Discoveryof Bioactive Substances (Marcel Dekker, Inc., New York, 1997); which isincorporated herein by reference to more fully describe the state of theart to which the present invention pertains.

A minaturization apparatus may be broadly classified into at least twocategories. A first category deals with micro-chemistry and involves theplacement of chemical substances in small amounts in sites formed onglass or a similar substance. These small amounts generally rangebetween picoliter and microliter aliquots. Such amounts shorten reactiontimes significantly over those conducted in reaction vessels holding onthe order a fraction of a milliliter, as currently achievable by a labtechnician working “by hand”. In addition to microchemical testing,levels of gene expression and protein levels can be tested on a largescale using micro-chemistry.

An example of this first category is the development of microplatetechnology in which a substrate (e.g. plastic) may include sitedensities of up to about many thousand (e.g. 96 to about 10,000) sites.This technology generally includes the use of complex micro-robotics orthe adaptation of ink-jet technology to apply chemical and biochemicalsubstances to chosen sites on the substrates. Frequently, at least oneof the reactants in a chemical assay to be performed is chemicallylinked to or otherwise immobilized at the reaction site, so that fluidsmay be added to and removed from the reaction site without removing anintermediate or end product of the reaction, since it is desirable thatthe intermediate or end product(s) is (are) to be retained at thereaction site, so that the outcome of the chemical assay may thereby bedetermined.

Currently, credit-card sized chips (e.g. glass chips) with greater thanmany thousand (e.g. 10,000) sites are in development (See Leach, 1997,Drug Discovery Today, 2:253). Each site may cover an area of 100 squaremicrons and may contain much less than 1 microliter in volume. The chipis a glass sandwich formed from individual glass layers, which are gluedtogether to form tubes to move substances between sites. The tubes aregenerally formed by cutting (e.g. etching), trenches or grooves in afirst glass layer and then sandwiching the trenches under a second glasslayer.

A second category of miniaturization apparatus (e.g. “lab on a chip”)employs silicon or glass as some functional modality in some functional(e.g. electrical or mechanical) modality as a substrate, and chemicalsthen are tested on the substrate. This category of apparatus may includethe use of electrokinetic motive forces. Micro-robotics ormicro-chemistry, or both, may be employed with such substrates,including the use of micro-fluidic pumps (pumps having no moving parts)to move substances between sites, the use of electrophoresis orelectrokinetic pressure pumping (a combination of electrophoresis andelectro-osmosis) as motive agents to analyze chemical reactions actingover the surface of the silicon substrate (for about e.g. 25 reactionsites).

Currently, to achieve high-throughput analyzing and screening techniquesfor chemical and biochemical reactions, complex operations usingcombinations of films and substrates or complex robotics for the preciseplacement of fluids carrying chemical compositions, or both arerequired. Such complex systems are subject to failure due to theirinherent complexity and are expensive to manufacture and maintain.

Moreover, current methods and systems for liquid sample processingconsume large amounts of expensive, toxic and specialty reagents. Thisis especially true in the pharmaceutical arts when throughput rates fora singe lab can be up to 100,000 samples per day, where each sampleincludes a volume on the order of 2-20 microliters.

Accordingly, it is desirable to be able to process hundreds or thousandsof liquid samples concurrently at a volume in the pico to micro literrange.

SUMMARY OF THE INVENTION

The devices and methods according to the present invention possess newcapacities and capabilities in liquid handling, storage, and dispensing.The present invention enables the storing of liquid samples in anyformat (including a conventional 96 sample format) for a period of time,and also allows for the dispensing of the liquid samples in minutevolumes. These volumes preferably range from picoliters to microliters.

Accordingly, the present invention provides a liquid handling device andmethod for storing and dispensing liquid samples in high density formatsusing liquid volumes with a range of several orders of magnitude.

The present invention also provides liquid handling devices and methodsusing a macro to micro interface and a new microelectro mechanicalsystem for real-time re-arraying of combichem and biochemical librariesand other liquid samples, as well as a means for compound storage,compound indexing, and compound dispensing.

The liquid handling devices and methods according to the presentinvention is particularly suited for re-arraying combichem andbiochemical libraries existing in 96 well formats into higher densityformats, e.g. 384 or 1536 well formats. Higher density formats (e.g.500,000, 1,000,000, and 2,000,000 samples) are within the scope of thisinvention.

Accordingly, in one aspect of the present invention, a liquid handlingsystem includes a liquid handling substrate having a plurality ofchannels for conducting a liquid sample. The channels terminate in acorresponding plurality of exit ports in an outer surface of thesubstrate for transfer of a quantity of the liquid sample. The liquidhandling system also includes a liquid storage and dispensing substratehaving a plurality of cartridges corresponding to the channels, wherethe cartridges terminate in a corresponding plurality of exit ports inan outer surface of the substrate for transfer of a quantity of theliquid sample. Each channel includes a reservoir in communication with acorresponding cartridge which creates an interface between the channeland the cartridge. Each cartridge terminates at a dispensing device. Thedispensing device may include a microelectro mechanical system (MEMS)comprising a membrane with an opening, a nozzle positioned adjacent tothe opening on a side of the membrane and a piezoelectric element.

Liquid is conveyed in the present invention using any one or acombination of means including capillary action, pneumatic means,electroosmotic flow, and a minipump.

In another aspect of the present invention, the liquid handling systemaccording to the above aspect may be used in a method having the stepsof drawing a liquid sample into the channels either by capillary action,pneumatic means, electoosmotic flow, a minipump or any combinationthereof, storing the liquid sample in the cartridges, and dispensing theliquid sample after a period of time.

Moreover, the above aspect may include further features including:

-   -   a liquid detecting means comprising a light emitting diode (LED)        and a photo-detector, for detecting a level of a liquid sample        in a cartridge;    -   a monolithic assembly of all cartridges;        -   separable cartridges, which may be separated using a            multifunctional head arrayed in either a fountain, roller,            conveyor belt or chain geometry;    -   electrical conductor(s) for supplying electrical energy to the        liquid detecting means and the liquid storage and dispensing        substrate; and    -   a registration mark and/or indexing mark on the outer surface of        the cartridge.

For a better understanding of the invention, reference is made to thebelow referenced drawings and written description following immediatelythereafter.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1A-1D are schematic diagrams of one embodiment of the liquidhandling system.

FIGS. 2A-2B are schematic diagrams of one embodiment of the cartridge ofthe liquid storage and dispensing substrate and the MEMS.

FIG. 3 is a schematic diagram of one embodiment of the liquid storageand dispensing substrate in which the cartridges are arranged in amonolithic array.

FIG. 4 is a schematic diagram of one embodiment of the liquid storageand dispensing substrate in which the separable cartridge are arrangedin a fountain geometry.

FIG. 5 is a schematic diagram of one embodiment of the liquid storageand dispensing substrate in which the separable cartridges are arrangedin a roller geometry.

FIG. 6 is a schematic diagram of one embodiment of the liquid storageand dispensing substrate in which the separable cartridges are arrangedin a conveyor belt geometry.

FIG. 7 is a schematic diagram of one embodiment of the liquid storageand dispensing substrate in which the separable cartridges are arrangedin a chain geometry.

DETAILED DESCRIPTION OF THE INVENTION

As shown in FIGS. 1A-1D, a macro interface includes 96 glass (or othercomparable material) capillary tubes 1 arrayed in a conventional 96sample format, fixed in place relative to one another. A correspondingmicro interface 11 includes 96 cartridges 12 fixed in place relative toone another by a holder. A liquid sample reservoir 3 is positionedbetween each capillary tube and corresponding cartridge. The array maybe arranged in any number of arrangements for yielding the desirednumber of tubes and cartridges. Such arrangements are illustrated inFIG. 1D 20-22.

FIGS. 2A-B, illustrate enlarged views of a cartridge 12 and amicro-electrical, mechanical system (MEMS) 4 positioned on one end ofthe cartridge. A liquid sample flows from the liquid handling substratethrough the reservoir into a lower part of the cartridge. Applying avacuum to orifice 23 forces liquid to enter the cartridge to “prime” thecartridge. Once the cartridge is primed, the liquid storage anddispensing substrate is inverted and both sides of the cartridge aresealed with an appropriate sealant to prevent evaporation,cross-contamination of the sample, and the introduction of particulatematter therein. A hydrophobic membrane 24 positioned adjacent theorifice 23 allows airflow into and out of the cartridge and prevents theliquid sample from being drawn out of the cartridge at the orifice 23.

A liquid sensing system monitors the liquid sample level in thecartridge. Using an LED 9, collimated light is sent through a narrowbleed passageway 25 that separates the MEMS 4 from the vacuum orifice23. When a liquid sample is present, light is refracted to aphotodetector 10 positioned on an opposite side of the bleed passageway25 from the LED 9. Light is refracted away from the photodetector 10,however, when the level of the liquid sample becomes too low afterdispensing of the liquid sample or if the device loses its prime and thebleed passageway 25 does not contain liquid.

Fluid flows from the lower part of the cartridge through a micro-filter26 (for removing particulate matter) as shown in FIG. 2B, so thatclogging of a silicon nozzle 7 at an exit orifice 6 is avoided. The exitorifice 6 is defined by a region surrounded by a silicon membrane 5,which is held in place by a glass substrate 27. The exit orifice andsilicon nozzle are created by micro-etching the silicon membrane.Coating the silicon membrane is a piezoelectric substance 8 that acts asan actuator for dispensing fluid. To dispense a fluid, the siliconnozzle points in a downward direction and electrical energy is suppliedto the piezoelectric substance. This causes the silicon membrane to flexand results in droplet ejection from the nozzle.

During assaying of the liquid sample, individual cartridges 12 may beseparated from other cartridges of the liquid storage and dispensingsubstrate. However, it is also possible to maintain the cartridges inthe same positions relative to one another creating a monolithicdispenser 11. Accordingly, each cartridge includes registration 18 andindexing marks 19 on the surface of the cartridges so that the cartridgemay be easily aligned and identified when the cartridges are separatedfrom one another. The cartridges are then fed in a serial manner into amultifunctional head reader 28.

The multifunctional head reader 28 includes an array of elements havingelectrical conductors 17 for supplying electrical energy to thecartridge 12 and an array of detectors 29 for determining the chemistryof the dispensed liquid samples. The head device may be designed in anynumber of geometries as indicated in the examples set forth below.

EXAMPLE 1 Multifunctional Head Device in a Fountain Geometry

As shown in FIG. 4, a fountain geometry 13 of individual cartridges 12are fed down through a set of tracks 30 arrayed across the assaysubstrate 31 in a spoke-like manner. Each of the tracks may house twobelts 32 on either side of a horizontal portion of the track. Cartridgesare drawn into the horizontal portion of the track via gravity and thenconducted across the surface of the substrate by the two belts on eitherside. The bottom and tops of the tracks may include air bearings or amaterial 33 with a low coefficient of friction to ease passage of thecartridges through the tracks. The tracks may also contain electricalconductors 17 that may run the length of the horizontal portion of thetrack or are split into discrete contact points. To dispense liquid,electrical energy is supplied to the electrical conductors 17 at anappropriate time when the cartridge 12 is positioned over a target. Toensure accurate positioning of the particular cartridge, the tracks mayinclude one or more sensors 37 to detect registration marks 18 and oneor more sensors 38 to detect indexing marks 19 provided on thecartridges. Sensors for chemistry detection 29 may also be used and maybe positioned on the underside of the tracks or placed on rails betweenthe tracks.

EXAMPLE 2 Multifunctional Head Device in a Roller Geometry

As shown in FIG. 5, roller geometry tracks 34 similar to those describedin Example 1 are arrayed in a cylindrical manner. Cartridges 12 arepositioned into the tracks 34 with the exit orifice 6 of each dispenserfacing outwards. Each track includes a row of cartridges which may bestaggered relative to one another at a pitch corresponding to reactionsites below or some multiple of the pitch. The cartridges may be lockedinto each track via a pressure plate applied to the open end to ensurethat each cartridge is snuggly positioned adjacent cartridges. Thisinsures proper alignment of the cartridges within the track. Eithercontiguous or discrete electrical conductors 17 or a combination of thetwo may be placed along the length of each track to provide electricalenergy to dispense liquid from an entire row of cartridges, individualcartridges in the row, or groups of cartridges within a row.Registration marks 18 on the cartridges may also be read via a detector37 to ensure proper registration of the cartridges with respect to theroller 14 and chemistry substrate 36. Dispensing is accomplished byrotating the roller 14 so that the appropriate track 34/cartridge 12 ispositioned over the reaction sites 36 and then energized via theelectrical conductors 17. Sensors 29 to detect chemical activity mayalso be used and positioned between the tracks, in another roller (adetection roller 35) or may be part of an overhanging arm positionedadjacent to the dispenser roller arm. In order to increase throughput,multiple rollers may also be used.

EXAMPLE 3 Multifunctional Head Device in a Conveyor Belt Geometry

As shown in FIG. 6, in the conveyor belt 15 geometry individualcartridges 12 are affixed to a conveyor belt 15 that transports eachcartridge 12 to its appropriate dispensing location. At the point ofalignment where the cartridge is horizontal, electrical conductors 17are in place to transmit electrical energy to actuate the dispenser.Additionally a sensor 37 may be placed adjacent to this point to ensureaccurate registration of the dispenser with respect to the reaction site36 below. A sensor 29 to detect chemical activity may also be placed atthis location.

EXAMPLE 4 Multifunctional Head Device in a Chain Geometry

As shown in FIG. 7, in the chain geometry 16 individual cartridges 12are linked male end 39 to female end 40 in a manner similar to that of abicycle chain. In essence the linked cartridges form a conveyor beltsimilar to that seen in Example 3, supra. By either using a sprocket andteeth system or a friction drive system the cartridges can be alignedwith respect to the reaction sites using a similar geometry andinstrumentation to that described supra in Example 3.

Having thus presented the present invention in view of the abovedescribed embodiments, various alterations, modifications andimprovements will readily occur to those skilled in the art. Suchalterations, modifications and improvements are intended to be withinthe scope and spirit of the invention. Accordingly, the foregoingdescription is by way of example only and is not intended to belimiting. The invention's limit is defined only in the following claimsand the equivalents thereto.

1-17. (canceled)
 1. A liquid handling system, comprising: a liquidhandling substrate having a plurality of channels for conducting aliquid sample, said channels terminating in a plurality of exit ports inan outer surface of said substrate for transfer of a quantity of saidliquid sample; and a liquid storage and dispensing substrate having aplurality of cartridges corresponding to said channels, said cartridgesterminating in a plurality of exit ports in an outer surface of saidsubstrate for transfer of a quantity of said liquid sample, wherein eachsaid channel includes a reservoir in communication with a correspondingcartridge creating an interface therebetween, and wherein each saidcartridge terminates at a dispensing device.
 2. The liquid handlingsystem of claim 1, wherein said cartridges comprise a monolithicassembly.
 3. The liquid handling system of claim 1, wherein saidcartridges are separable.
 4. The liquid handling system of claim 1,wherein the plurality of channels number up to approximately
 1536. 5.The liquid handling system of claim 1, wherein the plurality of channelsnumber approximately 96, 384 or
 1536. 6. The liquid handling system ofclaim 3, wherein said cartridges are separated using a multifunctionalhead, said head arrayed in a fountain, roller, conveyor belt or chaingeometry.